Physical layer frame format for WLAN

Abstract

A first format according to which a PHY data unit is to be generated is selected. The data unit is generated according to the first format, including generating a PHY preamble of the PHY data unit to include a first field and a second field. The PHY preamble is generated so that one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble to signal the first format. Or, the first field is generated to include a set of bits that according to an error detection scheme that does not conform to a second format; or the set of information bits indicates a mode not supported in connection with the second format. Or, a duplicate of at least one of the first field and the second field is included in the PHY preamble, to signal the first format.

What is claimed is: 
     
       1. A method for generating a data unit for transmission via a communication channel, the method comprising:
 selecting, at a communication device, a first format according to which the data unit is to be generated, the first format selected from a plurality of formats; 
 selecting, at the communication device, a pilot sequence to be used for generating the data unit, wherein
 the pilot sequence is selected from a plurality of pilot sequences corresponding to the plurality of data unit formats, 
 the pilot sequence is selected based on the selected first data unit format, 
 selecting the pilot sequence includes selecting a parameter c n,k  based on the selected first data unit format, 
 c n,k  is a sequence for an n-th orthogonal frequency division multiplexing (OFDM) symbol, and 
 k is an OFDM subcarrier index; 
 
 generating, at the communication device, the data unit according to the first format, including generating a physical layer (PHY) preamble according to the first format, wherein generating the PHY preamble includes generating the PHY preamble to include a first signal field and a second signal field, and wherein generating the PHY preamble further includes:
 generating one or more OFDM symbols of the PHY preamble according to the sequence c n,k , and 
 generating the PHY preamble to include the selected pilot sequence, modulated on one or more pilot subcarriers, in the one or more OFDM symbols; and 
 
 wherein generating the PHY preamble further includes at least one of:
 i) generating the PHY preamble so that one or more orthogonal frequency division multiplexing (OFDM) symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, 
 ii) generating, at the communication device, the first signal field to include a set of one or more information bits, and wherein generating the first signal field includes one or both of (a) generating the set of one or more information bits according to an error detection scheme that does not conform to a second format, and (b) generating the set of one or more information bits to indicate a mode not supported in connection with the second format, and 
 iii) including, at the communication device, a duplicate of at least one of the first signal field and the second signal field in the PHY preamble, 
 
 wherein the presence of the selected pilot sequence, modulated on the one or more pilot subcarriers, in the one or more OFDM symbols of the PHY preamble, and the at least one of:
 i) the one or more OFDM symbols that are rotated by 90 degrees with respect to the other OFDM symbols in the PHY preamble, 
 ii) the set of one or more information bits in the first signal field in the PHY preamble that is at least one of (a) generated according to the error detection scheme that does not conform to the second format, and (b) indicates the mode not supported in connection with the second format, and 
 iii) the duplicate of the at least one of the first signal field and the second signal field in the PHY preamble, 
 
 indicates to receiver devices that the data unit conforms to the first format among the plurality of formats. 
 
     
     
       2. The method of  claim 1 , wherein:
 at least some of the plurality of data unit formats correspond to different communication protocols; 
 the first format corresponds to a first communication protocol and a second format corresponds to a second communication protocol; and 
 at least one of
 i) the error detection scheme does not conform to the second communication protocol, 
 ii) the set of one or more information bits are generated to indicate a mode not supported by the second communication protocol, 
 iii) preambles of data units that conform to the second communication protocol do not include a duplicate of the first signal field nor a duplicate of the second signal field, and 
 iv) the second communication protocol does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble. 
 
 
     
     
       3. The method of  claim 2 , wherein:
 the second signal field follows the first signal field in the PHY preamble; and 
 at least one of:
 i) the error detection scheme does not conform to the second communication protocol, and 
 ii) the set of one or more information bits are generated to indicate a mode not supported by the second communication protocol. 
 
 
     
     
       4. The method of  claim 2 , wherein:
 preambles of data units that conform to the second format do not include the selected pilot sequence. 
 
     
     
       5. The method of  claim 4 , wherein:
 the first communication protocol defines a third format different than the first format; and 
 at least one of
 i) the error detection scheme does not conform to the second communication protocol, 
 ii) the error detection scheme does not conform to the third format, 
 iii) the set of one or more information bits are generated to indicate a mode not supported by the second communication protocol, 
 iv) the set of one or more information bits are generated to indicate a mode not supported by the third format, 
 v) the second communication protocol does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, 
 vi) the third format does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, and 
 vii) preambles of data units conforming to the third format do not include the selected pilot sequence. 
 
 
     
     
       6. An apparatus, comprising:
 a network interface device having one or more integrated circuits (ICs) configured to:
 select a first format according to which a data unit is to be generated, the first format selected from a plurality of formats, and 
 select a pilot sequence to be used for generating the data unit, wherein
 the pilot sequence is selected from a plurality of pilot sequences corresponding to the plurality of data unit formats, 
 the pilot sequence is selected based on the selected first data unit format, 
 selecting the pilot sequence includes selecting a parameter c n,k  based on the selected first data unit format, 
 c n,k  is a sequence for an n-th orthogonal frequency division multiplexing (OFDM) symbol, and 
 k is an OFDM subcarrier index; 
 
 
 wherein the one or more ICs are further configured to: 
 generate the data unit according to the first format, including generating a physical layer (PHY) preamble according to the first format, wherein generating the PHY preamble includes generating the PHY preamble to include a first signal field and a second signal field, and wherein generating the PHY preamble further includes:
 generating one or more OFDM symbols of the PHY preamble according to the sequence c n,k , and 
 generating the PHY preamble to include the selected pilot sequence, modulated on one or more pilot subcarriers, in the one or more OFDM symbols; and 
 
 wherein generating the PHY preamble further includes, at least one of:
 i) generating the PHY preamble so that one or more orthogonal frequency division multiplexing (OFDM) symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, 
 ii) generating the first signal field to include a set of one or more information bits, and wherein generating the first signal field includes one or both of (a) generating the set of one or more information bits according to an error detection scheme that does not conform to a second format, and (b) generating the set of one or more information bits to indicate a mode not supported in connection with the second format, and 
 iii) including a duplicate of at least one of the first signal field and the second signal field in the PHY preamble, 
 
 wherein the presence of the selected pilot sequence, modulated on the one or more pilot subcarriers, in the one or more OFDM symbols of the PHY preamble, and the at least one of:
 i) the one or more OFDM symbols that are rotated by 90 degrees with respect to the other OFDM symbols in the PHY preamble, 
 ii) the set of one or more information bits in the first signal field in the PHY preamble that is at least one of (a) generated according to the error detection scheme that does not conform to the second format, and (b) indicates the mode not supported in connection with the second format, and 
 iii) the duplicate of the at least one of the first signal field and the second signal field in the PHY preamble, 
 
 indicates to receiver devices that the data unit conforms to the first format among the plurality of formats. 
 
     
     
       7. The apparatus of  claim 6 , wherein:
 at least some of the plurality of data unit formats correspond to different communication protocols; 
 the first format corresponds to a first communication protocol and a second format corresponds to a second communication protocol; and 
 at least one of
 i) the error detection scheme does not conform to the second communication protocol, 
 ii) the set of one or more information bits are generated to indicate a mode not supported by the second communication protocol, 
 iii) preambles of data units that conform to the second communication protocol do not include a duplicate of the first signal field nor a duplicate of the second signal field, and 
 iv) the second communication protocol does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble. 
 
 
     
     
       8. The apparatus of  claim 7 , wherein:
 the second signal field follows the first signal field in the PHY preamble; and 
 at least one of:
 i) the error detection scheme does not conform to the second communication protocol, and 
 ii) the set of one or more information bits are generated to indicate a mode not supported by the second communication protocol. 
 
 
     
     
       9. The apparatus of  claim 7 , wherein:
 wherein preambles of data units that conform to the second format do not include the selected pilot sequence. 
 
     
     
       10. The apparatus of  claim 9 , wherein:
 the first communication protocol defines a third format different than the first format; and 
 at least one of
 i) the error detection scheme does not conform to the second communication protocol, 
 ii) the error detection scheme does not conform to the third format, 
 iii) the set of one or more information bits are generated to indicate a mode not supported by the second communication protocol, 
 iv) the set of one or more information bits are generated to indicate a mode not supported by the third format, 
 v) the second communication protocol does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, 
 vi) the third format does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, and 
 vii) preambles of data units conforming to the third format do not include the selected pilot sequence. 
 
 
     
     
       11. A method, comprising:
 receiving, at a communication device, a data unit via a communication channel, wherein the data unit includes a physical layer (PHY) preamble, and wherein the PHY preamble further includes a first signal field and a second signal field; 
 determining, at the communication device, a pilot sequence modulated on one or more pilot subcarriers of one or more orthogonal frequency division multiplexing (OFDM) symbols of the PHY preamble; and 
 determining, at the communication device, a format of the data unit from among a plurality of formats that the communication device is configured to recognize, wherein determining the format of the data unit includes identifying, at the communication device, the pilot sequence, modulated on the one or more pilot subcarriers, of the PHY preamble from a plurality of pilot sequences corresponding to a plurality of data unit formats, wherein identifying the pilot sequence comprises identifying a sequence c n,k , wherein n is an OFDM symbol index and k is an OFDM subcarrier index; 
 wherein determining the format of the data unit further includes at least one of:
 i) determining whether one or more orthogonal frequency division multiplexing (OFDM) symbols in the PHY preamble are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, wherein PHY preambles according to the format include the one or more OFDM symbols rotated by 90 degrees, and PHY preambles of one or more other formats do not include the one or more OFDM symbols rotated by 90 degrees, 
 ii) determining whether a set of one or more information bits in the first signal field is at least one of (a) generated according to an error detection scheme specified by the format and not specified by one or more other formats, and (b) indicates a mode supported by the format and not supported by one or more other formats, and 
 iii) determining whether the PHY preamble includes a duplicate of at least one of the first signal field and the second signal field, wherein PHY preambles according to the format include the duplicate of the at least one of the first signal field and the second signal field, and PHY preambles of one or more other formats do not include the duplicate of the at least one of the first signal field and the second signal field. 
 
 
     
     
       12. The method of  claim 11 , wherein:
 the format corresponds to a first communication protocol and one or more other formats correspond to one or more second communication protocols; 
 determining the format of the data unit includes at least one of
 i) determining that the error detection scheme conforms to the first communication protocol and does not conform to at least one of the one or more other second communication protocols, 
 ii) determining that the set of one or more information bits indicate a mode supported by the first communication protocol and not supported by at least one of the one or more other second communication protocols, 
 iii) determining that the PHY preamble includes the duplicate of at least one of the first signal field and the second signal field, wherein preambles of data units that conform to at least one of the one or more other second communication protocols do not include a duplicate of the first signal field nor a duplicate of the second signal field, and 
 iv) determining that one or more OFDM symbols in the PHY preamble are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, wherein at least one of the one or more other second communication protocols does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble. 
 
 
     
     
       13. The method of  claim 12 , wherein:
 the second signal field follows the first signal field in the PHY preamble; and 
 determining the format of the data unit includes at least one of:
 i) determining that the set of one or more information bits in the first signal field is generated according the error detection scheme, wherein the error detection scheme does not conform to at least one of the second communication protocols, and 
 ii) determining that the set of one or more information bits indicate a mode not supported by at least one of the second communication protocols. 
 
 
     
     
       14. The method of  claim 12 , wherein:
 preambles of data units that conform to at least one of the second communication protocols do not include the pilot sequence. 
 
     
     
       15. The method of  claim 14 , wherein:
 the format is a first format; 
 the first communication protocol defines a second format different than the first format; and 
 at least one of
 i) the error detection scheme does not conform to at least one of the second communication protocols, 
 ii) the error detection scheme does not conform to the second format, 
 iii) the set of one or more information bits are generated to indicate a mode not supported by at least one of the second communication protocols, 
 iv) the set of one or more information bits are generated to indicate a mode not supported in connection with the second format, 
 v) at least one of the second communication protocols does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, 
 vi) the second format does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, and 
 vii) preambles of data units conforming to the second format do not include the pilot sequence. 
 
 
     
     
       16. An apparatus, comprising:
 a network interface device having one or more integrated circuits (ICs) configured to:
 receive a data unit via a communication channel, wherein the data unit includes a physical layer (PHY) preamble of the data unit, and wherein the PHY preamble further includes a first signal field and a second signal field, 
 determine a pilot sequence modulated on one or more pilot subcarriers of one or more orthogonal frequency division multiplexing (OFDM) symbols of the PHY preamble, and 
 determine a format of the data unit from among a plurality of formats that the communication device is configured to recognize, wherein determining the format includes identifying, at the communication device, the pilot sequence, modulated on the one or more pilot subcarriers, of the PHY preamble from a plurality of pilot sequences corresponding to a plurality of data unit formats, wherein identifying the pilot sequence comprises identifying a sequence c n,k , wherein n is an OFDM symbol index and k is an OFDM subcarrier index: 
 
 wherein determining the format of the data unit further includes at least one of:
 i) determining whether one or more orthogonal frequency division multiplexing (OFDM) symbols in the PHY preamble are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, wherein PHY preambles according to the format include the one or more OFDM symbols rotated by 90 degrees, and PHY preambles of one or more other formats do not include the one or more OFDM symbols rotated by 90 degrees, 
 ii) determining whether a set of one or more information bits in the first signal field is at least one of (a) generated according to an error detection scheme specified by the format and not specified by one or more other formats, and (b) indicates a mode supported by the format and not supported by one or more other formats, and 
 iii) determining whether the PHY preamble includes a duplicate of at least one of the first signal field and the second signal field, wherein PHY preambles according to the format include the duplicate of the at least one of the first signal field and the second signal field, and PHY preambles of one or more other formats do not include the duplicate of the at least one of the first signal field and the second signal field. 
 
 
     
     
       17. The apparatus of  claim 16 , wherein:
 the format corresponds to a first communication protocol and one or more other formats correspond to one or more second communication protocols; 
 the one or more ICs are configured to at least one of
 i) determine that the error detection scheme conforms to the first communication protocol and does not conform to at least one of the one or more other second communication protocols, 
 ii) determine that the set of one or more information bits are generated to indicate a mode supported by the first communication protocol and not supported by at least one of the one or more other second communication protocols, 
 iii) determine that the PHY preamble includes the duplicate of the first signal field or the duplicate of the second signal field, wherein preambles of data units that conform to at least one of the one or more other second communication protocols do not include a duplicate of the first signal field nor a duplicate of the second signal field, and 
 iv) determine that one or more OFDM symbols in the PHY preamble are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, wherein at least one of the one or more other second communication protocols does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble. 
 
 
     
     
       18. The apparatus of  claim 17 , wherein:
 the second signal field follows the first signal field in the PHY preamble; and 
 the one or more ICs are configured to at least one of:
 i) determine whether the set of one or more information bits in the first signal field is generated according the error detection scheme, wherein the error detection scheme does not conform to at least one of the second communication protocols, and 
 ii) determine whether the set of one or more information bits indicate a mode not supported by at least one of the second communication protocols. 
 
 
     
     
       19. The apparatus of  claim 17 , wherein:
 preambles of data units that conform to at least one of the second communication protocols do not include the pilot sequence. 
 
     
     
       20. The apparatus of  claim 19 , wherein:
 the format is a first format; 
 the first communication protocol defines a second format different than the first format; and 
 at least one of
 i) the error detection scheme does not conform to at least one of the second communication protocols, 
 ii) the error detection scheme does not conform to the second format, 
 iii) the set of one or more information bits are generated to indicate a mode not supported by at least one of the second communication protocols, 
 iv) the set of one or more information bits are generated to indicate a mode not supported in connection with the second format, 
 v) at least one of the second communication protocols does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, 
 vi) the second format does not specify that the one or more OFDM symbols are rotated by 90 degrees with respect to other OFDM symbols in the PHY preamble, and 
 vii) preambles of data units conforming to the second format do not include the pilot sequence.